1. Field of the Invention
This invention relates to a sound outputting apparatus such as a headphone apparatus and a portable telephone terminal and also to a sound outputting method and a sound output processing program for use with the apparatus as well as a sound outputting system which includes a headphone apparatus and a sound outputting apparatus.
2. Description of the Related Art
In order to acoustically reproduce a reproduction sound signal of a portable audio player so that a listener listens to the sound, usually a headphone apparatus or an earphone apparatus is used such that sound may not leak to the outside.
However, sound leaking from a headphone apparatus has become a social problem as noise or disagreeable sound in an electric train or the like in recent years. Generally, sound leakage from a headphone apparatus in most cases occurs when the reproduction sound volume is set to a comparatively high level by a listener to listen to the reproduction sound.
Against the program just described, a technique of automatically suppressing the maximum sound volume on the audio player side or anther technique of suppressing the reproduction sound pressure using a compressor process or a limiter process has been proposed. The latter technique is disclosed, for example, in Japanese Patent No. 3,016,446 (Japanese Patent Laid-Open No. Hei 05-49091, hereinafter referred to as Patent Document 1).